Posted by Square root on Tuesday, October 16, 2012 at 8:43pm.
Memorize the common square roots
2 * 2 = 4
3 * 3 = 9
etc.
Then using those squares, you can estimate other square roots.
Example:
square root of 130 =
√ 121 = 11
√ 144 = 12
√ 130 is between 11 and 12
Ok. Is there an easy way to figure the perfect square root for numbers 13 through 25.
3 * 3 = 9
4 * 4 = 16
5 * 5 = 25
Memorize the squares of 1 - 12
So are u saying to memorize the squares for 13 - 25 as well? Not sure if my question is clear. For e.g. square of 23 is 529. By multiplying the last digit of 23 ( 3x3)= 9, same last digit of the number 529, is there a way I easily work out the first 2 numbers 52?
ahh, so you want to square the numbers , not take their square roots
A mental way to multiply any two 2-digit numbers
e.g.
34 x 34
4x4 = 16 , so the last digit is 6 , with 1 to carry
3x4+ 4x3 = 24 plus the one to carry is 25
so the tens digit is 5 , with 2 to carry
3x3 = 9 with 2 to carry is 11
so 34^2 = 1156
the numbers don't have to be the same ...
e.g. 56 x 83
6x3 = 18 , so unit digit is 8 , carry 1
5x3 + 6x8 = 63 , so tens digit is 4 , carry 6
5x8 = 40, plus the carry 6 = 46
56x83 = 4648
but really, am I not just doing the steps of ordinary multiplication ??